This invention relates, in the production of a porous cross-linked polymer, preferably a porous cross-linked polymer having open cells formed continuously both on the surface and through the interior thereof, by the horizontal continuous polymerization of a water in oil type high internal phase emulsion (hereinafter occasionally abbreviated briefly as xe2x80x9cHIPExe2x80x9d), to a technique concerning the mode, shape and structure, and material of a weir utilizing non-Newtonian and thixotropic viscosity of the HIPE for the sake of preventing the HIPE from leaking, enabling the formed polymer to acquire and retain a necessary thickness throughout to the opposite end parts, preventing the polymer from failing to cure owing to the decrease in an oxygen supply, and permitting the formed polymer to retain a superposed sheet such as an upper film.
This invention also relates to a novel method for the production of a porous cross-linked polymer, preferably a porous cross-linked polymer having open cells formed continuously both on the surface and through the interior thereof, by the horizontal continuous polymerization and curing in a polymerizing furnace of an HIPE using a supporting member on the lower side and a sheet material on the upper side and also to a technique for obtaining a porous cross-linked polymer as a cured product enjoying improved surface smoothness and excelling in accuracy of thickness.
Further, this invention relates to a technique for supplying an HIPE to an apparatus for the horizontal continuous polymerization, shaping the HIPE, and controlling the thickness of the formed HIPE for the sake of effecting the horizontal continuous polymerization of the HIPE with satisfactory accuracy of thickness and also to a novel method for producing by this technique a porous cross-linked polymer, preferably a porous cross-linked polymer having open cells formed continuously both on the surface and through the interior thereof.
The term xe2x80x9cshapingxe2x80x9d as used in the specification refers to an action of converting a shapeless mass into a mass of a prescribed shape; the term xe2x80x9ccontrolling the thicknessxe2x80x9d refers to an action of converting a shapeless mass into a mass of a prescribed shape (i.e., shaping) and imparting a prescribed thickness to the mass of the prescribed shape; and the term xe2x80x9caccuracy of thicknessxe2x80x9d refers to the deviation and error concerning the prescribed thickness.
Concerning the gasket for the production of a methyl methacrylate (occasionally referred to briefly as xe2x80x9cMMAxe2x80x9d) resin plate by the continuous cast polymerization of a polymerizing syrup centering on MMA, a Newtonian fluid having a low viscosity, U.S. Pat. No. 3,872,197, U.S. Pat. No. 3,988,098, JP-B-60-31,643, etc. have disclosed methods which, by means of gaskets adapted to be used as compressed, produce a plate having a thickness in the approximate range of 25 to 50% of the outer diameter of the relevant tube of the gasket. These methods, however, entail problems of failing to impart a desired thickness to the produced resin plate because the gasket in use is formed of a soft resin and is consequently susceptible of deformation caused by the clamping force or heat and a problem of increasing dispersion of the plate thickness. Concerning the gasket fit for the cast polymerization that involves the cell cast polymerization and the continuous cast polymerization, JP-A-5-253,951, JP-A-5-329,847, etc., while proposing the improvements in shape, structure, and material for the gasket of the kind as mentioned above, have disclosed methods for using gaskets similarly adapted to be used as compressed and producing a plate having a thickness in the approximate range of 30 to 90% of the outer diameter of the relevant tube of gasket. Incidentally, the cast polymerization has not been proposed for the use in the polymerization of an HIPE, a non-Newtonian, thixotropic and viscous fluid. Naturally, no proposal has ever been made as to the weir that includes a gasket for the use in the cast polymerization.
The methods for producing a porous cross-linked polymer by the polymerization of an HIPE have been disclosed, for example, in WO 97/27240, WO 97/37745, etc.
WO 97/27240 discloses as a method for the production of a porous cross-linked polymer by the polymerization of an HIPE using a film, a method for the combined continuous and batch polymerization which comprises continuously packing a vertical band-shaped zippered bag made of a resin film with an HIPE, reeling the packed bag, and then polymerizing the HIPE in the bag batchwise. Further, WO 97/37745 discloses a method for the production of a porous cross-linked polymer which comprises coating an HIPE on a porous substrate (such as a felt), causing at least part of the HIPE to impregnate the porous substrate, and polymerizing the HIPE deposited on the substrate.
The method for polymerizing an HIPE as disclosed in WO 97/27240, however, entails the problem of failing to make the most of the advantage of the continuous packing step because the operation from packing through polymerization of the HIPE cannot be carried out continuously and consequently because the transitional stage between the step for continuous packing of HIPE and the step for batch polymerization constitutes itself a rate-determining process. Further, since the operation from packing through polymerization of the HIPE is not carried out continuously, the film selected for the use in this method leaves out of consideration about durability at elevated temperatures and capability of recyclic use as well. This method also entails the problem of imposing limits on height (width) and thickness of the bag, encountering difficulty in retaining uniformity of thickness and performance quality of the bag, and failing to control the width and the thickness freely, because the lower part of the bag tends to gain in thickness under the weight of the HIPE and, to make the matter worse, because the oil phase and the liquid phase of the HIPE tend to deflect and separate vertically from each other, despite the belief that the lower part of the bag begins to thicken as compared with that at the time of packing the HIPE and the uniformity of thickness of the bag is exalted slightly in consequence of the reeling operation. This method, owing to the use of the bag made of film, further entails the problem of failing to obtain a porous cross-linked polymer which is possessed of varied properties on the opposite surfaces, though it barely obtains a porous cross-linked polymer possessed of identical properties both on the surfaces.
WO 97/37745 states that the polymerization may be performed batchwise or continuously, whichever may suit the occasion better. It has absolutely no typical proposal regarding a process for the continuous production of an HIPE using a porous substrate and a polar material in combination.
The films disclosed in the conventional techniques have respectively definite qualities as described above. No typical proposal of any sort has ever been made concerning the selection of a film which is excellent in durability (resistance to heat, resistance to the action of monomer, resistance to hydrolysis, and capability of recycling) fit for the polymerization at elevated temperatures and capable of controlling the surface properties of a porous cross-linked polymer (such as smoothness, ability to form open cell structure, and resistance to occurrence of pinholes and voids).
(1) Technique Concerning Coating
The coating technique exists which continuously applies a liquid substance on a supporting member being advanced as retained horizontally (such as a belt conveyor and a film advanced through a horizontally set path).
The term xe2x80x9ccoatingxe2x80x9d used herein is defined as xe2x80x9capplying on a substrate a layer intended for coating, finishing, or protecting either or both of the opposite surfaces of the substratexe2x80x9d (Coating and Laminating: published by Kako Gijutsu Kenkyusho).
The industrial coating technique has been aimed mainly at forming a thin film on a substrate. The coating materials generally adopted for this technique are an emulsion, a liquid resin, a polymer melt, etc.
The conditions which are generally applied to the coating are shown below (Reference: xe2x80x9cCoating Methodsxe2x80x9d published by Maki Shoten).
Coating speed: up to 1000 m/min
Coating mass: up to 200 g/m2 (based on specific gravity as 1, applied in a thickness of 200 xcexcm at a coating rate of 200 g/m2)
Viscosity of coating: 0.01 to 100 Pa.s (usually a Newtonian fluid)
Method for coating: Various coaters are used often
Leveling property: Automatically leveled by gravity to form a flat surface owing to the Newtonian property.
(2) Technique Concerning Acrylic Casting
The continuous forming of an acrylic cast plate is available as a technique for continuously spraying a compound on a supporting member adapted to be advanced as horizontally retained, for example, a steel belt.
This technique forms a coat of a larger thickness (approximately up to 15 mm) as compared with the technique of coating.
The resin component is an acrylic syrup which is a Newtonian fluid.
Typically, U.S. Pat. No. 4,019,811 discloses a method for regulating a thickness of a coat by continuous forming of an acrylic cast sheet.
The method disclosed in this publication is claimed to effect the regulation of thickness by means of double steel belts, specifically by injecting resin melt between opposed rigid objects.
The method is claimed to deprive the upper belt of sag by applying hydraulic pressure to retain a prescribed distance between the opposed belts. This distance between the belts consequently corresponds to the thickness of the acrylic cast sheet.
The resin itself has no ability to retain the thickness of itself unless it is placed to fill the closed space (except after the solidification). By the regulation of thickness as mentioned above and the application of hydraulic pressure, the resin is enabled to retain its thickness.
The amount of the resin to be supplied is not controlled. The resin is eventually supplied in a prescribed amount.
As a means for the continuous formation of an acrylic cast sheet, JP-A-3-68,605 also discloses a method which comprises supplying a resin of high viscosity through an extruding device or a die (in spite of unusually high viscosity) meanwhile imparting shape thereto.
This publication has a remark, reading xe2x80x9cthe thickness of the polymer is usually decided at the point of departure from the die. It is only the amount of the resin to be supplied that is decided. The thickness and the shape of the sheet of resin, however, are decided by the distance between the opposed steel belts after all.
Despite a mention purporting unnecessities of providing the upper belt with a retaining device, the action of retaining the upper belt is actually implemented with a liquid, a semi-solid, or a solid. That is, the hydraulic pressure contemplated by the invention of U.S. Pat. No. 4,019,811 has given place to the viscosity of liquid, the rigidity of a semi-solid, or the rigidity of a solid.
Further, since the method of this publication mentioned above uses an extruding device, a die, or double steel belts, the apparatus for implementing the method has a huge and expensive construction.
The resin itself has no ability to retain the thickness and the shape of itself at the stage of departure in a hot molten state from the die. It is simply difficult to move (to be fluidized) because of its high viscosity.
The present inventors, therefore, have made a diligent study with a view to overcoming the problems to be encountered by the method for producing a porous cross-linked polymer by the polymerization of the HIPE identified above. They have consequently perfected a method for the production of a porous cross-linked polymer, which is capable of controlling the surface properties of the porous cross-linked polymer, permitting free control of the width and the depth of the polymer, and continuously carrying out the operation ranging from supplying through polymerizing the HIPE. Specifically, they have found that in the method for the production of a porous cross-linked polymer by the polymerization of an HIPE, the problems mentioned above can be solved by causing the outer surface of the HIPE by a means for decreasing an oxygen content to assume an atmosphere or a state having a lower oxygen content than an ambient air and continuously performing steps from the supplying through the polymerization of the HIPE, preferably continuously performing the steps from the supplying through the polymerization of the HIPE in the horizontal method (namely by subjecting the HIPE to horizontal continuous polymerization).
Unlike the conventional method for the combined continuous and batch polymerization which comprises batchwisely polymerizing an HIPE and subsequently slicing the produced polymer in a fixed thickness, the method for the horizontal continuous polymerization of an HIPE mentioned above is targeted at generously curtailing the process of production by continuously carrying out a series of operations ranging from supplying through polymerization of an HIPE thereby effecting the impartation of a necessary thickness to the produced polymer. The novel method for the horizontal continuous polymerization of an HIPE which has been perfected by the present inventors has originated in the discovery that the success in securing at such a stage of manufacture a formed polymer in process having a thickness of unusually high accuracy constitutes an important and new technical task, i.e. a task peculiar to the method for the horizontal continuous polymerization.
Further, the present inventors, in appreciation of the fact that adoption of cast polymerization has not been proposed concerning the polymerization of a thixotropic and viscous HIPE which is a non-Newtonian fluid and that no suggestion has been made concerning the weir including a gasket for cast polymerization, have pursued a diligent study on the horizontal continuous polymerization of a non-Newtonian, thixotropic, and viscous HIPE, with a view to establishing a technique for producing an HIPE polymer while preventing the HIPE from leaking, enabling the formed polymer to acquire and retain a necessary thickness, preventing the HIPE from escaping polymerization owing to a decrease in oxygen supply, and enabling the formed polymer to retain a superposed sheet such as an upper film. As a result, they have acquired a knowledge that, in the method for producing a porous cross-linked polymer by the horizontal continuous polymerization of an HIPE, the object mentioned above can be attained by using a weir at each of the sides of the HIPE supporting member along the width direction.
They, however, have found that the process for the horizontal continuous polymerization of an HIPE mentioned above poses another technical task concerning the thickness of the sheet material along the width direction because {circle around (1)} the sheet material, after entering a furnace for the polymerization and curing, sags under its own weight and induces a change in thickness, {circle around (2)} the deflection of the sheet material under its own weight is constant and the deviation thereof, therefore, grows in proportion to the decrease in the thickness aimed at, and {circle around (3)} the deflection mentioned grows in proportion as the width (forming width) for injecting an HIPE increases.
They further have found that the process for the horizontal continuous polymerization of an HIPE mentioned above poses such a new technical task concerning the travel direction (the direction of flow) of the polymerization line as that {circle around (1)} the tensile force in the direction of flow of the sheet material placed in the furnace is decided by the roll in the HIPE-injecting part and the roll mounted on the outlet side of the furnace for the polymerization and curing and this tensile force, when suffered to grow to an unduly large extent, gathers wrinkles in the sheet material and these longitudinal wrinkles deprive the HIPE surface of smoothness and impart an undulating state to the finished product and this phenomenon gains in conspicuousness because of the viscous quality (great thixotropy) of the HIPE and {circle around (2)} when two vertically opposed nip rolls which will be specifically described herein below are adopted in the resin-injecting part for the purpose of controlling thickness and combining sheet materials and when the feeding speed (rotation rate) of the nip rolls is larger than the speed of reeling the sheet materials, the insertion of the sheet materials proceeds excessively and invokes the surface of the porous cross-linked polymer as the polymerized product to gather lateral wrinkles.
It is, therefore, an object of this invention to provide for the production of a porous cross-linked polymer by the horizontal continuous polymerization of an HIPE which can improve the smoothness of flat surface and the accuracy of thickness of the produced polymer.
To be more specific, in a series of operations of imparting an HIPE with high accuracy to a supporting member being moved as retained horizontally (such as a belt conveyor or a sheet material moved as retained in a horizontal state), superposing a sheet material on the upper surface of the superposed HIPE layer, and curing the resultant HIPE in a polymer curing furnace, this invention is to provide a method for obtaining a porous cross-linked polymer as a polymerized and cured product while enabling the HIPE to retain an accurately formed cross-sectional shape (smooth flat surface and accurate thickness) even when it is held inside the curing furnace.
In addition to the objects described above, this invention has another object of providing a method for improving the HIPE ""s ability to intercept air at the opposite end parts thereof.
In the solution of such important and new technical tasks as pointed out above, it has been ascertained that the conventional coating techniques and acrylic casting techniques mentioned above differ in many points from the method for the horizontal continuous polymerization of an HIPE and, therefore, cannot be applied in their unmodified form to the method of interest.
That is, the method for horizontal continuous polymerization of an HIPE, though different from the conventional coating techniques in terms of the kind of object to be handled, constitutes itself a technique for applying an HIPE (non-Newtonian fluid) in an unusually large thickness (to a maximum of approximately 100 mm) under the following conditions.
Line speed: 0.1 to 100 m/min
Amount of supply: Maximum 100 kg/m2 (in the case of the thickness of 100 mm)
Viscosity: Incapable of unique definition on account of thixotropy (non-Newtonian, function of shear rate)
Self-leveling: The self-leveling under gravity occurs only with difficulty or consumes time because the HIPE is an apparently solid or unusually viscous liquid at zero shear.
Thus, in the case of the HIPE, the accuracy of thickness is not easily secured because the formation of a flat surface by the self-leveling occurs only with difficulty. It has been ascertained consequently that the horizontal continuous polymerization must be performed by securing the accuracy of thickness at the stage for supply and impartation of shape.
Conversely, since the formed polymer has an ability to retain the imparted shape by itself, it is capable of retaining the thickness and the shape even after the polymerization. It has been consequently ascertained that the horizontal continuous polymerization has no need for such an expensive and massive device as double steel belts.
When the horizontal continuous polymerization of an HIPE is compared with the conventional coating and acrylic casting techniques in the light of the various points mentioned above, the following contrasts are revealed.
Coating mass: Horizontal continuous polymerization of HIPE, Acrylic cast sheet greater than  greater than Coating
Coating viscosity: Non-Newtonian vs. Newtonian
Leveling property: Absence of leveling property vs. Self-leveling property
Retention of thickness: Self-retaining property vs. No bearing on retention of thickness because of retention by external force or thinness of film
The conventional coating technique and acrylic casting technique differ in many points from the method for horizontal continuous polymerization of an HIPE and, therefore, cannot be applied in their unmodified form to the method of interest. In a novel process for the horizontal continuous polymerization of an HIPE, this invention has yet another object of providing a novel method for obtaining a porous cross-linked polymer of a thickness of extremely high accuracy notwithstanding the HIPE (non-Newtonian fluid) is applied in a very large thickness (to a maximum of approximately 100 mm) at the stage of production which constitutes itself an important and new technical task.
More specifically, in a novel process for the horizontal continuous polymerization of an HIPE, this object of the present invention resides in providing a novel method for obtaining a porous cross-linked polymer of a thickness of high accuracy by supplying the HIPE to an apparatus for the horizontal continuous polymerization and performing impartation of shape and regulation of thickness on the HIPE thereby effecting the horizontal continuous polymerization of the HIPE in a thickness of satisfactory accuracy.
For the purpose of accomplishing the objects as mentioned above, the present inventors have pursued a series of studies diligently concerning the method for the polymerization of a thixotropic and viscous HIPE which is a non-Newtonian fluid. This invention has been perfected as a result.
Specifically, the objects of this invention can be accomplished by (1) a method for the production of a porous cross-linked polymer by the horizontal continuous polymerization of a water-in-oil high internal phase emulsion, which comprises using a weir one each at the opposite end parts in the width direction of an emulsion supporting member for the use in the horizontal continuous polymerization of the emulsion.
Further, the objects of this invention can be accomplished by (2) the method for production set forth in (1) above, wherein the height of the weir is in the range of 0.5 to 100 mm.
Further, the objects of this invention can be accomplished by (3) the method for the production of a porous cross-linked polymer set forth in (1) or (2) above, wherein a supporting member is used on the lower side of the emulsion and a sheet material on the upper side thereof for performing the horizontal continuous polymerization of the emulsion and a tensile force is exerted in the width direction and/or the travel direction of the sheet material.
Further, the objects of this invention can be accomplished by (4) the method set forth in (3) above, wherein the tensile force is exerted by a tension roller, a pin tenter, or a clip tenter in the width direction of the sheet material.
The other objects of this invention can be further accomplished by (5) the method for production set forth in (3) or (4) above, wherein either a thickness imparting roll or a reeling device provided with a nip roll comprising a driven roll and a drive roll vertically opposed across a space and further provided with a torque control mechanism in the reeling part on the outlet side of a polymerization furnace is disposed in the part for injecting the emulsion on the inlet side of the polymerization furnace relative to the travel direction of the sheet material for the purpose of adjusting the tensile force in the travel direction.
Further, the other objects of this invention can be accomplished by (6) the method for production set forth in any one of (1) to (5) above, wherein the thickness of the emulsion is regulated by passing the emulsion between a movable supporting member and an object disposed so as to retain a prescribed distance from the movable supporting member.
The objects of this invention can be also accomplished by (7) the method for production set forth in (6) above, wherein a plurality of such objects as mentioned above are arranged in the travel direction of the movable supporting member.
Further, the other objects of this invention can be accomplished by (8) the method for production set forth in any one of (1) to (5) above, wherein a die is used in the supply part for the emulsion as a means for spreading the emulsion in the width direction of the movable supporting member.
Furthermore, the objects of this invention can be accomplished by (9) a method for production of a porous cross-linked polymer, which comprises a method set forth in (6) or (7) above in combination with a method set forth in (8) above.
For the purpose of solving the new technical tasks mentioned above, the present inventors have pursued a series of studies diligently concerning the method for producing a porous cross-linked polymer by the horizontal continuous polymerization of an HIPE and have consequently perfected the following invention. They have further discovered that the combinations of this invention with the invention described above may be also useful.
Specifically, the objects of this invention can be accomplished by (10) a method for the production of a porous cross-linked polymer by the horizontal continuous polymerization of a water-in-oil high internal phase emulsion, which comprises using a supporting member on the lower side of the emulsion and a sheet material on the upper side thereof for performing the horizontal continuous polymerization of the emulsion and performing the polymerization by exerting a tensile force in the width direction and/or the travel direction of the sheet material.
The objects of this invention can be also accomplished by (11) the method for production set forth in (10) above, wherein the tensile force is exerted by a tension roller, a pin tenter, or a clip tenter in the width direction of the sheet material.
The other objects of this invention can be accomplished also by (12) the method for the production set forth in (10) or (11) above, wherein either a thickness imparting roll or a reeling device provided with a nip roll comprising a driven roll and a drive roll vertically opposed across a space and further provided with a torque control mechanism in the reeling part on the outlet side of a polymerization furnace is disposed in the part for injecting the emulsion on the inlet side of the polymerization furnace relative to the travel direction of the sheet material for the purpose of adjusting the tensile force in the travel direction.
The other objects of this invention can be further accomplished by (13) the method for production set forth in any one of (1) to (12) above, wherein the thickness of the emulsion is regulated by passing the emulsion between a movable supporting member and an object disposed so as to retain a prescribed distance from the movable supporting member.
The other objects of this invention can be also accomplished by (14) the method for production set forth in (13) above, wherein a plurality of such objects as mentioned above are arranged in the travel direction of the movable supporting member.
The other objects of this invention can be further accomplished by (15) the method for production set forth in any one of (10) to (12) above, wherein a die is used in the supply part for the emulsion as a means for spreading the emulsion in the width direction of the movable supporting member.
The other objects of this invention can be further accomplished by (16) a method for the production of a porous cross-linked polymer, which comprises a method set forth in (13) or (14) above in combination with a method set forth in (15) above.
For the purpose of accomplishing the objects as mentioned above, the present inventors have pursued a diligent study in search of a novel method for the horizontal continuous polymerization of an HIPE and have consequently acquired a knowledge that the thixotropic (non-Newtonian) qualities of the HIPE can be utilized advantageously and effectively for enabling the horizontal continuous polymerization of the HIPE with satisfactory accuracy of thickness. The present invention has been perfected based on this knowledge. They have further discovered that the combinations of this invention with the invention described above may be likewise useful.
Specifically, the objects of this invention can be accomplished by (17) a method for the production of a porous cross-linked polymer by the horizontal continuous polymerization of a water-in-oil high internal phase emulsion, which comprises effecting the regulation of thickness of the emulsion by passing the emulsion between a movable supporting member and an object disposed so as to retain a prescribed distance from the movable supporting member.
The objects of this invention can be also accomplished by (18) the method for production set forth in (17) above, wherein a plurality of such objects as mentioned above are arranged in the travel direction of the movable supporting member.
The other objects of this invention can be accomplished also by (19) a method for the production of a porous cross-linked polymer by the horizontal continuous polymerization of a water-in-oil high internal phase emulsion, which comprises using a die in the supply part for the emulsion as a means for spreading the emulsion in the width direction of the movable supporting member.
The other objects of this invention can be further accomplished by (20) a method for the production of a porous cross-linked polymer, which comprises a method set forth in (17) or (18) above in combination with a method set forth in (19) above.